This invention relates to packaging, and more particularly to packaging of perishable food products.
In packaging of fresh red meat products, it is known to initially cut and package the meat products at a processing facility for subsequent shipment to retail outlets. Typically, the meat products are packaged such that ambient air is contained within the package, which can result in discoloration of the meat product caused by conversion of myoglobin meat pigment to a grayish or brownish metmyoglobin. This discoloration generally renders the meat product unacceptable for consumers. Ultimately, such exposure to ambient air can result in spoilage of the meat product.
In order to avoid discoloration and spoilage of meat products and to provide a desirable aging of the meat product, it is known to vacuum package the meat product to remove ambient air and any other atmosphere from the package. It is also known to package the meat product in an inert gas atmosphere, such as a nitrogen gas atmosphere.
Vacuum packaging of meat products is less than optimal for several reasons. First, vacuum packaging is a relatively expensive process requiring specialized equipment. Secondly, vacuum packaging produces an end product in which the film wrap material is in contact with the meat product, resulting in an irregularly shaped package which is undesirable from the standpoint of product presentation. Further, vacuum packaged meat products do not have the deep red color desired by consumers.
Packaging fresh meat products with an inert gas atmosphere has been found to be an acceptable way to preserve the meat product and provide a desirable aging, after shipment of the meat product from a processing facility to a retail outlet. However, once the package has arrived at the retail outlet, it is necessary to replace the inert gas atmosphere within the package with an oxygen-containing atmosphere. This removes any discoloration on the surface of the meat product which may have been caused by the presence of the inert gas atmosphere, and produces the desired oxygen "bloom" which results in the desirable deep red color on the surface of the meat product.
U.S. Pat. No. 4,055,672 issued Oct. 25, 1977 discloses a system in which a meat product is packaged within a package in which one of the package walls is formed from a gas impermeable material and another package wall is formed of an inner gas permeable layer and an outer gas impermeable layer. The meat product is initially packaged in an inert gas atmosphere, which is maintained within the package by the package walls including the outer gas impermeable wall layer. When it is desired to display the meat product for purchase by a consumer, the outer gas impermeable layer is removed, which enables oxygen-containing ambient air to flow into the package through the gas permeable layer. This results in the desired oxygen bloom in preparation for display. This system is disadvantageous in that deterioration of the product is not prevented after the impermeable layer has been removed, unless an additional impermeable layer is subsequently added to the package. In addition, it is necessary to add an impermeable layer over the permeable layer if the product is to be frozen. Further, the required combination of a gas impermeable film layer overlying a gas permeable film layer is difficult and expensive to produce, and difficult to seal to the container in a manner providing satisfactory removal of the gas impermeable layer.
U.S. Pat. No. 4,919,955 issued Apr. 24, 1990, discloses a packaging system in which a septum valve is incorporated into the wall of a tray in which the meat product is packaged. A hollow needle is inserted through the septum valve and is interconnected with an atmosphere exchange device, which functions to remove the inert gas atmosphere from the interior of the package and replace it with an oxygen-containing atmosphere, to induce the desired oxygen bloom in the meat product. After the atmosphere within the package is exchanged, the hollow needle is removed and the septum valve closes to maintain the oxygen-containing atmosphere within the package. Again, this system is functional to replace an inert gas atmosphere with an oxygen-containing atmosphere in the interior of a package. However, the septum valve provides a point of entry for possible tampering with the package contents while the package is on display, which would not leave any trace of tampering on the package itself. Further, the hollow needle terminates in a sharp end which could give rise to hazardous conditions for the operator of the atmosphere exchange device.
It is an object of the present invention to provide a packaging system for perishable products in which an inert gas atmosphere within the interior of the package can be easily and quickly replaced with an oxygen-containing atmosphere. It is a further object of the invention to provide such a packaging system in which the final package is identical in appearance to prior art packages from a consumer standpoint. It is a further object of the invention to provide such a packaging system in which the packaged product can be frozen without having to add an additional layer of wrap material to the package. Yet another object of the invention is to provide such a packaging system in which the atmosphere within the package interior is replaced using an oxygen-containing atmosphere delivery apparatus which does not present the potential for harm to an operator. A still further object of the invention is to provide such a packaging system in which the final package configuration is not susceptible to undetectable tampering.
In accordance with one aspect of the invention, an atmosphere exchange method is provided for a perishable food product package in which the food product is disposed within a receptacle having an internal cavity and an inert gas atmosphere is contained within the receptacle cavity, and in which a substantially impermeable film is sealed to the receptacle to maintain the inert gas atmosphere within the receptacle cavity. The atmosphere exchange method of the invention involves forming an opening in a portion of the seal between the film and the receptacle, replacing the inert gas atmosphere within the receptacle cavity, through the opening, with a non-inert gas atmosphere, and sealing the film to the receptacle to close the opening and to maintain the non-inert gas atmosphere within the receptacle cavity. The receptacle preferably includes a side wall having an upper surface including a lateral projection. The step of forming the opening in the seal between the film and the receptacle is carried out by first sealing the film to an outer portion of the lateral projection while leaving an inner portion of the lateral projection unsealed, and subsequently removing at least the outer portion of the lateral projection such that the opening is formed between the film and the inner unsealed portion of the lateral projection. The upper surface of the receptacle side wall is sealed to the film on either side of the lateral projection to define a pair of aligned spaced sealed areas, and the step of removing at least the outer portion of the lateral projection is carried out such that the opening is located between the pair of aligned, spaced sealed areas. The step of replacing the inert gas atmosphere within the receptacle cavity is carried out by separating the film from the side wall upper surface at the unsealed area to form the opening, and introducing the non-inert gas atmosphere into the receptacle cavity interiorly of the opening and simultaneously enabling the inert gas to escape the receptacle cavity through the opening. The step of introducing the non-inert gas atmosphere into the receptacle cavity is carried out utilizing a nozzle having a discharge area, and inserting the nozzle through the opening such that the nozzle discharge area is disposed interiorly of the opening and in communication with the receptacle cavity. The nozzle occupies less than the entire area of the opening, such that the unoccupied portion of the opening creates an outlet passage establishing communication between the receptacle cavity and the exterior of the receptacle for allowing the inert gas atmosphere to escape from the package interior upon introduction of the inert gas atmosphere. The step of separating the film from the side wall upper surface at the unsealed area is carried out by stretching the film between the spaced sealed areas to allow the nozzle to pass through the opening. The film at the unsealed area then returns to its original, unstretched condition subsequent to removal of the nozzle, and the step of sealing the film to the receptacle to close the opening is carried out by sealing the film to the receptacle at the previously unsealed area between the sealed areas. With this arrangement, the atmosphere within the package is exchanged and the package has the external appearance of any conventional fresh meat product packaged within a tray-type receptacle having an impermeable film overwrap sealed thereto.
In accordance with another aspect of the invention, a package for use in packaging a perishable food product is in the form of a receptacle defining an internal cavity and having a peripheral sealing surface, and a film sealed to the peripheral sealing surface. The receptacle includes a tab portion, and the peripheral sealing surface includes a non-linear segment in which the film is sealed to the tab portion. The receptacle further includes a sealing area located inwardly of the non-linear segment of the sealing surface and substantially coplanar with spaced portions of the sealing surface on either side of the non-linear segment. With this construction, the tab and the film secured to the non-linear segment can be removed to create an unsealed area between the film and the receptacle for use in exchanging the atmosphere within the receptacle cavity. After the atmosphere has been exchanged, the film is sealed to the sealing area to close the opening. The sealing area extends substantially linearly between the spaced portions of the sealing surface on either side of the non-linear segment. The receptacle preferably has a series of side walls extending upwardly from a bottom wall, and each side wall includes a sealing flange located at its upper end. The tab extends outwardly from the sealing flange of one of the side walls, such that the peripheral sealing surface is defined by the sealing flanges in combination with the tab. The tab is preferably in the form of a planar extension of one of the sealing flanges, and preferably has a length less than the length of the sealing flange from which it extends. The sealing flange on either side of the tab defines the spaced linear segments of the peripheral sealing surface between which the non-linear segment is located. In a preferred form, the sealing flange and the tab are configured such that removal of the tab between the spaced linear segments of the peripheral sealing surface results in a sealing flange substantially identical in configuration to a sealing flange associated with at least one other side wall of the receptacle.
In accordance with another aspect of the invention, a receptacle for use in packaging a perishable food product includes a bottom wall and a series of side walls extending upwardly therefrom to define an internal cavity for receiving the perishable food product. The upstanding side walls define a peripheral sealing surface adapted to have a film sealed thereto for closing the internal cavity. At least at first one of the side walls includes a lateral projection having an outer edge defining a portion of the sealing surface and an inner area substantially coplanar with the outer edge and with spaced portions of the sealing surface adjacent the lateral projection. The first side wall includes a sealing flange defining a portion of the peripheral sealing surface, and the lateral projection extends from the sealing flange and is substantially coplanar therewith. The first side wall and its associated sealing flange have a length greater than that of the lateral projection.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.